Central Rice Research Institute Annual report...2011-12

Enhancing and Sustaining the Productivity of Rice Based Farming Systems
Long term–assessment of
soil quality and resilience
in rice-rice system
The long term effect of nutrient
management practices on soil
physical, chemical and biological
properties was studied for
proper interpretation of the yield
changes and development of soil
quality indices. Keeping this, in
view after 41 years of rice-rice
system, the detailed soil analysis
was conducted to find out the
effects of nutrient management
practices on soil properties in a
subtropical rice–rice system.To
determine a soil quality index,
sustainable yield index was
taken as the goal. The minimum
data set (MDS) of indicators that
best represent soil function were
selected and scoring of MDS indicators
based on their performance
of soil function was done.
Finally indicator scores were integrated
into a comparative index of soil quality. The
value of the dimensionless soil quality index varied
from 1.46 in control plot to 3.50 in NPK +FYM plot. Six
soil quality indicators such as DTPA Zn, SOC, available
N, CDI, DHA and available K contributed 21.4,
20.4, 18.0, 19.5, 16.6 and 4.1% to the soil quality index
estimation, respectively under NPK +FYM treated plot
(Fig. 21). By considering NPK+FYM as an ideal treatment,
the relative soil quality explained that if there
were exclusion of FYM, the soil quality would decline
by 31.4%; similarly if no manure and fertilizers were
applied, the soil quality would decline by 61.4%. Similarly
when compared with NPK treatment, soil quality
declined by 47.3, 35.8, 5.7 and 14.0% in control, N, NP
and NK treatments. This indicated that N and FYM are
the important interventions which maintain and improve
the soil quality.
Management of Problem Soils
Management of coastal saline soils
Soil samples were collected during post monsoon
period from Ersama block, Jagatsingpur district of
Odisha during 2011-12 in a grid size of 4 km x 4 km.
The soil pH, EC (1:2), available N, Available P, avail-
Fig. 21. Relative contribution of soil quality indicators to the soil quality
index of long term rice–rice soil under different nutrient management
systems
able K and micronutrients were determined. Crop cutting
experiments were conducted in wet season at some
places proximity to the grid point to determine the yield
of rice under N applied and no N applied plots, the
grid points where crop cutting was not possible secondary
data from the farmers were collected. Taking
the soil properties, salinity status and historical data
i.e. waterlogged and non waterlogged conditions; the
agronomic N use efficiency was assigned for each grid
points. The site specific fertilizer N (SSFN) required was
calculated using the formulae SSFN = (Y Target
– Y 0
N)/
AEN, Y Target
= Yield target, Y 0
N = N-limited yield, AEN
= Expected plot grain yield increase per unit of fertilizer
N applied. The data of soil EC and site specific
fertilizer N required were subjected to analysis of classical
statistics and the data fitted well to normal distribution.
The EC value ranged from 0.25 dSm -1 to 6.04
dSm -1 with average value of 1.43 dSm -1 . The SSFN ranged
from 66-100 kg ha -1 with an average of 80 kg ha -1 . Using
appropriate semivariograms, the EC (1:2) and SSFN
value were interpolated by kriging with the given grid
size; the map generated (Fig. 22) provided the regions
and loops of EC and with distinct values and explains
the quality and heterogeneity in the region.
CRRI ANNUAL REPORT 2011-12
67